Molecular Dynamics Simulations Indicate Aromaticity as a Key Factor in the Inhibition of IAPP_(20-29) Aggregation

Islet amyloid polypeptide (IAPP) is a 37-residue amyloidogenic hormone implicated in the progression of Type II Diabetes (T2D). T2D affects an estimated 422 million people yearly and is a comorbidity with numerous diseases. IAPP forms toxic oligomers and amyloid fibrils that reduce pancreatic β-cell mass and exacerbate the T2D disease state. Toxic oligomer formation is attributed, in part, to the formation of interpeptide β-strands comprised of residues 20-29 (IAPP_(20-29)). Flavonoids, a class of polyphenolic natural products, have been found experimentally to inhibit IAPP aggregate formation. Many of these small flavonoids differ structurally only slightly; the influence of functional group placement on inhibiting the aggregation of the IAPP_(20-29) has yet to be explored. To probe the role of small-molecule structural features that impede IAPP aggregation, molecular dynamics simulations were performed to observe trimer formation on a model fragment of IAPP_(20-29) in the presence of morin, quercetin, dihydroquercetin, epicatechin, and myricetin. Contacts between Phe23 residues were critical to oligomer formation, and small-molecule contacts with Phe23 were a key predictor of β-strand reduction. Structural properties influencing the ability of compounds to disrupt Phe23-Phe23 contacts included aromaticity and carbonyl and hydroxyl group placement. This work provides key information on design considerations for T2D therapeutics that target IAPP aggregation.